1. Related Application
The present application is related to and claims priority to PCT Application Serial No. PCT US99/29770, International Filing Date of Dec. 15, 1999, and Priority Date of Dec. 17, 1998, which is incorporated herein by reference for all purposes.
2. The Field of the Invention
This invention relates to carpet cleaning generally, and more particularly to portable, self-contained pumping and heating systems for carpet cleaning. More particularly still, the invention relates to a cleaning system that uses heated cleaning solution where the heat is derived from secondary heat of a primary heat-generating engine, which also provides mechanical force used to deliver and remove the cleaning solution during cleaning.
3. The Background Art
Ever since carpets came into common use, people have wrestled with the difficulty of keeping them clean. Carpet, unlike other fabric in household use, is exposed to an enormous amount of foreign matter such as dirt, grass, leaves, sand, dust, mud, animal hair, and spilled food. The problem is compounded by both the permanent (e.g. wall-to-wall) installation of carpet and the length of fibers found in many carpets. Permanent (e.g. wall-to-wall) installation requires on-site cleaning. Bundles or yarns comprised of many fibers tend to capture or adhere to soiling, such as particulate matter. Conventional washing and cleaning processes remain ineffective.
xe2x80x9cHot-water extractionxe2x80x9d methods have been developed to facilitate carpet-cleaning. Hot water may actually include liquid water; saturated, two-phase, steam and water droplets; or superheated steam. The latter is not commonly relied upon, since it is typically hotter than the distortion temperature of synthetic fibers. Moreover, the energy requirements for the phase change to steam simply cannot be met by most heating plants for the purpose.
According to these methods, water is heated, pressurized, supplemented with chemical cleaning additives and applied to carpet in order to dissolve or release soils and particulates and to suspend the resulting matter in the water (e.g. solvent, carrier, etc.). A xe2x80x9cvacuumxe2x80x9d system then extracts the dissolved soils, suspended particulates, and water out of the fibers. The water and air flows drawn by the vacuum system entrain the entire mixture, carrying it to a holding tank.
Because the majority of soiling in textiles is oil and acid based, textile cleaning machine operators rely on basic solutions for cleaning agents. Also, because temperature greatly affects the processes of dissolving and chemical reactions, the higher the temperature of a cleaning fluid, the more effective the cleaning process. The water should preferably be at about 210xc2x0 F. at the carpet surface. When water is substantially cooler, machine operators compensate by increasing the pressure, chemical content, or quantity of the cleaning fluid, or some combination thereof.
Pressure translates to fluid velocity, which affects penetration of fiber bundles (yarns) by the fluid. Higher velocity fluid may also better strip soils from fibers mechanically. Mechanical agitation may improve rates of dissolving by a solvent, and may reduce boundary layers near fibers for improved chemical reaction.
Water-based carpet cleaning may apply or leave excess water standing in carpets, or retained by surface tension therein. Excess water tends to damage carpets by soaking into areas over time, causing over-wetting. Over-wetted textiles often show signs of reduced strength, mildew, and delamination, a process in which the carpet takes on a rippled appearance due to separation of primary and secondary backings.
Excessive concentrations of chemicals (typically alkaline) may increase reaction rates for dissolving or removing soils, by removing binding agents adhering them to carpets. However, increasing chemical concentrations creates a whole new series of problems. Alkaline chemicals may remove or discolor pigments in carpet, remove stain-resisting treatments, void manufacturers"" warranties, and attack fibers, glues, or backing materials"" structural integrity. Also, cleaning chemicals are known to leave residues that cause carpet to re-soil at an accelerated rate by adhering to soiling materials.
Increased cleaning fluid temperatures increase chemical reaction rates, allowing textile cleaners to decrease the concentration of chemicals, the fluid pressure, and the fluid quantity used in the cleaning process. If the temperature of the cleaning fluid is high enough, soils can be removed even without chemical additives, high fluid pressure, or large quantities of fluid. The result is still somewhat chemical in nature, since water is a xe2x80x9csolventxe2x80x9d for many naturally occurring materials. Also, temperature can affect diffusion of water into a material to be dissolved, and diffusion of dissolved materials in a structure, just as with other chemical processes.
Increasing the cleaning fluid temperature may change the thermodynamics of the application and drying process. For example, if less time is required to apply a high-speed spray of droplets, less soaking can occur. Also, the thermodynamic quality of the water in a high pressure jet may be increased, providing increased steam to break up water into smaller droplets, and to augment the air flow moving away form the cleaned carpet yarns. Less water residence time, and smaller particle sizes for water droplets result in entrainment of more liquid in the vacuum drawn pickup line. Likewise, higher energy content, less water, and less residence time means faster drying time. Thus, the risk of de-lamination, mold growth, tensile strength loss, and other ill effects of moisture is reduced. Instead, carpet is left with low moisture and a more neutral pH.
For effective cleaning, cleaning fluid temperatures must not only be high, but consistent. Since the effectiveness of any hot-water extraction method depends greatly on the fluid temperature, an inconsistent fluid temperature results in a carpet that appears patchy because it is cleaner in some places than in others. In addition, temperatures in excess of 240xc2x0 F. can permanently yield synthetic fibers, thereby causing fiber memory loss and ruining the pile texture of carpet.
Several different types of hot-water extraction systems have been developed in the carpet cleaning industry. xe2x80x9cPortablexe2x80x9d systems are moved into a building and transported from room to room by an operator. They typically use household electricity and water supplies to run motors and heaters needed to heat, apply, and remove water. As a result, they provide inferior cleaning temperatures, typically in the range of 80xc2x0 to 120xc2x0 F. at the carpet surface. Portable machines are notorious for excessive use of chemicals. High chemical concentrations are required to clean textiles because of comparatively low cleaning temperatures.
xe2x80x9cTruck-mountedxe2x80x9d textile cleaning equipment may be of an xe2x80x9cintegralxe2x80x9d type, also known as xe2x80x9cdirect drivexe2x80x9d type (dependent on the automotive power plant for energy), or of a xe2x80x9cslide-inxe2x80x9d type (standalone). Each has its own set of performance and maintenance problems.
Direct drive systems marketed today rely exclusively on heat extracted from the engine coolant (radiator water). The result is that the best heat exchangers and transfer times do not produce a maximum cleaning fluid temperature above 195xc2x0 F. in the heat exchanger, which temperature is substantially reduced by the time fluid reaches a carpet surface.
Integrated, direct drive systems rely on the coolant of an internal combustion engine to provide heat to the cleaning fluid. They rely on the fan belts of the vehicle engine for mechanical power. Such systems can provide comparatively high vacuum power, but temperatures typically range from 100xc2x0 to 170xc2x0 F. at the carpet surface. Since they take energy from the coolant that passes through the vehicle radiator, they provide an inconsistent, and still too low fluid temperature at the carpet surface. A lot of energy is available from the engine coolant, but at a low thermodynamic availability.
The fan belt from a typical utility van drives a shaft running from the vehicle engine, between the vehicle seats, to the bed of the van to power the pump and vacuum equipment. Unfortunately, large, high torque (e.g. V-8), gasoline-powered engines, were not designed to run stationary at 1500 RPM for hours at a time just to drive the fan belt while carpet cleaners perform their work. Without a consistent convective air flow, gasoline engines idling for lengthy periods of time tend to create enormous amounts of radiant heat that which destroys electrical components and leads to reliability problems.
Although sometimes a significant improvement over portable systems, and slide-in units, the integrated, truck-mounted systems can also dump substantial waste heat and vibrational energy into the vehicle. They tend to destroy the vehicle body, wear out the engine, and damage its electrical equipment and mechanical connections. These problems have been exacerbated during recent years by the introduction of electronic components and controls about the cab and engine bay of modem vehicles. Electrical and electronic components degrade near heat sources. The result is a continuing degradation and failure of electrical and electronic components. Such failures regularly render the engine inoperative until the failed component is replaced.
xe2x80x9cSlide-inxe2x80x9d machines typically depend on a small gasoline engine to power equipment, all installed in a common utility vehicle such as a van. Process heat is taken from the heat rejected by the engine. As with direct-drive systems, the equipment compartment (bed) and cab of a van become very hot when the engine is run in stationary mode with only the confined, standard, inadequate cooling system. The unit is also nearly impossible to isolate mechanically from the body of the vehicle. As a practical matter, slide-in systems literally self-destruct during a comparatively short and very unreliable life.
Thus, these self-contained, slide-in systems are generally regarded as even more problematic and unreliable than direct drive systems. Poor reliability and durability should come as no surprise because of the extraordinary amounts of heat rejected by the engines into the environment. Moreover, the net thermal energy output is still typically too low to support the amount of water flow required for a high rate of cleaning.
Stationary (e.g. slide-in) engines are not designed and operated at the efficiencies common to current automotive power plants. When the engines of slide-in units have been selected to have thermal outputs to support higher temperatures at the required water flow rates, the fuel efficiency is still extremely poor, and the environmental heat rejection problem is even more serious.
The exhaust temperature for a gasoline internal combustion engine may be as high as 1400xc2x0 F. The temperature difference above that of the cleaning fluid, and thus the thermodynamic availability, is initially adequate. However, for a small engine (e.g. slide-in unit), the mass flow rate of exhaust is very low, so overall heat transferred to the cleaning fluid is also low.
Auxiliary heating is a method tried for improving performance of direct-drive systems. Despite their increased mechanical power, currently available direct drive machines remain incapable of maintaining a consistently high cleaning fluid temperature. Use of external heating devices may raise the top-end temperature. However, use of auxiliary burners, such as propane, kerosene, diesel, and electric burners, has been declining in recent years.
External heating is cumbersome, inconvenient to set-up, expensive, and possibly even dangerous due to the possibility of fire or overheating. However, some carpet-cleaning professionals persist in using external heating machines because the co-generating devices (capturing waste heat from a thermodynamic engine to use as process heat) typically cannot produce a sufficiently high temperature (over 170xc2x0 F. at the carpet, over 195xc2x0 F. in the system), sufficient efficiency, nor an acceptable level of reliability.
Several other details related to the foregoing comparisons are noteworthy. For example, the fuel consumption characteristics of car and truck engines have been regulated by the Environmental Protection Agency since 1971. As a result, manufacturers have developed the cycle timing, fuel-to-air ratios, and cylinder dimensions of vehicle engines to greatly decrease the amount of fuel required to provide a given power output. However, stationary engines for comparatively unregulated, limited use, such as those found in slide-in systems, have not been optimized to the same extent. As a result, larger slide-in motors consume a great deal of fuel without providing a comparable amount of power or rejected heat required for process heating.
Technically, both slide-in units and direct-drive systems are co-generation plants, since a single engine provides process heat and mechanical output. Nevertheless, perhaps the most serious problem for co-generation systems is the failure of their control systems. Valves, whether driven by solenoids or vacuum, quickly foul with calcium, lime, magnesium, and other precipitates. Meanwhile, the high environmental temperatures inherent in such systems destroy the electrical and electronic control components.
Vehicle engines on direct-drive machines produce comparatively more rejected heat to the radiator, at low availability, while exhausting the combustion gases to ambient. Direct drive, co-generation machines lack any safe, reliable, and convenient method for conveying the cleaning fluid and the exhaust through a heat exchanger. Bringing an engine exhaust line into an enclosed rear cabin of a vehicle, together with the pumping equipment and cleaning fluid, is dangerous. An inevitable opening or leak in the exhaust pipe would fill the vehicle with exhaust gases, which are toxic, corrosive, and possible even highly combustible.
Likewise, extending a cleaning fluid line outside the cabin of a van or other service vehicle to access and exhaust line is not a viable solution. Any water-based cleaning fluid left in the line in cold weather will freeze when the engine is not running, bursting the line.
Exhaust gases from an internal combustion engine vary significantly in temperature due to changes in the combustion rate and temperature of the engine. In addition, the amount of heat transferred by exhaust must be distributed over some amount of cleaning fluid. Cleaning fluid moving comparatively slowly through a heat exchanger during a time of less use of such fluid by an operator, will absorb more heat and exit the exchanger at a comparatively higher temperature. If an operator stops to move furniture, reposition equipment, or make a dry pass to vacuum up excess cleaning fluid, the flow rate of cleaning fluid through a washing plant will slow or stop. The resulting temperatures and pressures can harm carpet, destroy equipment, and cause personal injury.
Perhaps most importantly, all co-generation systems that rely on exhaust gases for top-end heat must jettison heated cleaning fluid in order to control temperatures and heat flow balances. Solutions expelling overheated cleaning fluid either out of the system or into a waste tank when it becomes too hot are inadequate. One drawback of such a safety device is that the cleaning fluid must be replenished before cleaning can resume. Also, jettisoned cleaning fluid wastes both heat and fluid. Anything vented to the holding tank reduces capacity, and must be dumped along with the collected soiled cleaning fluid. Thus, dump valve systems are inconvenient and potentially harmful to the environment. Every day, thousands of gallons of cleaning fluid are wasted in the carpet cleaning industry due to cleaning fluid venting performed in the name of temperature regulation.
Devices that shut down the system are similarly inconvenient, and often not safe. A failure in a temperature regulating mechanism can allow the fluid temperature to continue rising to dangerous levels. Meanwhile, the electrical and electronic control elements, such as sensors, solenoids, and valves, used to detect excessive temperatures and bleed off cleaning fluid or shut down the system are prone to failure. Control orifices can be very small and are subject to clogging from calcium, lime, and magnesium deposits from the cleaning fluid. The high temperatures involved accelerate the buildup of deposits and can damage the wire coils and insulation, causing failure in items such as solenoids. Valve failures can cause catastrophic failure of the entire system.
One more problem that plagues known washing plants involves the method by which mechanical power is transferred from the vehicle engine to the pumps and heaters. Current direct drive systems are driven by a shaft coupled to a fan belt of the engine. No carpet cleaning system is known to use any power takeoff coming directly from the engine or from a transmission or transfer case. Transmissions are delicate and expensive. Just as engines are overworked, and improperly worked in such an application, gear systems would be overworked and be subject to mechanical failures due to repeated engagement and disengagement of the PTO gears if operated to control connection of mechanical systems to engine power.
A great need exists for a direct drive washing plant capable of capturing heat from both the radiator coolant and engine exhaust gases. Such a washing plant should provide high cleaning fluid temperatures necessary for effective particulate release, solution, or suspension as required. The system needs to be freezing-safe in virtually all weather, yet not damage vehicle structure or electronics. Operator safety is also needed, against exposure to exhaust gases, or pressure failures. A need also exists for a failsafe temperature regulation mechanism. The mechanism should permit heat exchange only when the entire system is active and functional, thereby preventing overheating in the event of a failure of any element in the heat transfer system or thermal and flow regulation mechanisms. A reliable PTO drive train is needed for transferring mechanical energy, but more importantly for engaging and disengaging frequently and reliably for many duty cycles.
According to the present invention, a transportable cleaning system is disclosed that utilizes a direct drive washing plant with an intermediate, nonfreezing fluid to transfer heat between engine exhaust and a cleaning fluid. A failsafe thermostat device regulates the temperature of the cleaning fluid without interrupting the cleaning process or wasting cleaning fluid.
A PTO for mechanical power can run full time at the engine or transfer case without gear engagement and disengagement. Instead, a PTO clutch is engageable downstream from the transmission or transfer case in the power train. Thus high, positive displacement, mechanical power can be output reliably from the transmission or transfer case, not jury-rigged from the fan belt. The downstream positioning of the clutch permits the PTO to be continuously engaged, thereby avoiding the shifting frequency problems that might otherwise be encountered. Also, any constantly rotating PTO shaft provided in a production truck can be accessed and used.
In certain embodiments, an apparatus and method in accordance with the present invention may include a diesel vehicle engine to power pumps and blowers pressurizing cleaning fluid and air supplies. A hydraulically or otherwise actuated clutch may provide access to a full-time PTO shaft. Multiple heat exchangers, and multiple loop heat exchangers, retrieving heat from both exhaust flows and engine coolant, provide comparatively higher temperatures for heating cleaning fluids, such as water-based fluids. The higher, cleaning-fluid temperatures can be obtained through higher thermodynamic availability, more net energy available, higher heating fluid temperatures, improved heat exchange staging, and improved heat transfer efficiencies. The apparatus and method of the present invention provide delivery of necessary quantities of heated water, or even-superheated (pressurized and heated over ambient boiling point) water, in sufficient quantities to support a carpet cleaning tool (e.g. wand), at temperatures greater than 195xc2x0 F. in the line and 170xc2x0 F. at the carpet. Temperature may approach the ambient boiling point, which may even be exceeded by design, if desired, in the pressurized cleaning fluid.
Increased cleaning fluid temperatures enable faster and more thorough cleaning of carpets and other surfaces. In addition, carpet dries faster when cleaned with superheated steam or water. The enhanced vacuum power of the current invention allows multiple operators with separate lines and wands to work from a single supply system on one truck. This decreases cleaning time, cuts labor costs, and minimizes inconvenience to customers. Substantially lower repair costs and downtime flow from a simpler design. In addition, the current invention provides a xe2x80x98multi-functionxe2x80x9d (e.g. steam cleaning and pressure washing) machine in accordance with new and newly proposed restrictions on hazardous waste dumping, promulgated by the EPA and other governmental agencies.
The integration of the cleaning system with the transport vehicle also possess a number of significant advantages over known washing plants. Legal seating is available for three instead of just two operators. Fuel consumption is lower per pound of heated cleaning fluid delivered. Adequate power is available to provide comparatively high mass flow rates of water for pressure washing at 2,000 psi.
Furthermore, more space and a higher weight capacity are available to support larger wastewater recovery tanks, thereby reducing the likelihood that hazardous materials will be dumped on streets or in storm drains accidentally or in relief valve operation. Less equipment set-up time is required because the vehicle has adequate space for cleaning fluid, tools, and other accessories. Since the vehicle carries its water on board, operators are free of the need to locate and connect to a water source (often an inadequate source) near each job site. The apparatus and method of the present invention are the only known means of eliminating the need to jettison needed water as a means of temperature control in co-generator heating systems. Since cleaning water is never jettisoned as a means for temperature control, the supply lasts longer and the waste tank does not fill up as fast. Since the exhaust flow is diverted to control overheating, the top-end cleaning fluid temperature is regulated without resorting to any manipulation of the heated water or heat exchanger performance.